You can never tell for certain from oral arguments, and there have been some surprise twists already in this case, but these comments don't sound encouraging for the federal exchange subsidies. A few excerpts - there's much more in the story:

"If legislation is stupid, I don't see that it's up to the court to save it," said Senior Judge A. Raymond Randolph...Randolph and Judge Thomas Griffith seemed inclined to side with foes of the law, who told the panel that lower-income people are only eligible for tax credits if they buy health insurance through an exchange established by a state - not one set up by the federal government...

...[Randolph] called the Affordable Care Act "a last-minute deal filled with a lot of predictions, even the title," and said the predictions have not been born out. "The launch was an unmitigated disaster," and the costs of implementation "have gone sky-high," he said. "Suppose Congress made another prediction" - that if the tax credits were conditioned on setting up exchanges "all the states would line up for this deal." But this prediction too was not borne out, he said.

..."The legislative history is a wash," Griffith said. "There doesn't seem to be any clear legislative history." Without evidence of congressional intent, Griffith said, "You have a special burden" to show that the plain language of the statute "doesn't mean what it appears to mean."

Randolph added, "What we've got here is language that doesn't seem malleable." If the court knows "the clear purpose of the statute" - in this case, to provide affordable health insurance - but Congress "didn't write it clearly enough, is it our job to fix the problem?," Griffith wondered.

Randolph said no. The court can overrule plain statutory language based on the "absurdity principle, but I don't see a stupidity principle."